MOSCOW -- Thousands of demonstrators have protested in downtown Moscow against the Russian government's efforts to block the popular Telegram messaging app.
Protesters at the rally on April 30 chanted: "[President Vladimir] Putin is a Thief!" and called for freedom on the Internet.
Opposition politician Alekei Navalny was one of thousands of people at the protest organized by the Libertarian Party of Russia, which has called the attempts to block Telegram "a national shame."
Protesters held posters calling on the government to stop its attempts to block Telegram, which fell afoul of the authorities over its refusal to give the Federal Security Service (FSB) access to users' private messages.
Libertarian party chief Sergei Boiko led protesters in calls to "stop censorship on the Internet!"
While it has met with mixed success, the bid to block Telegram has deepened concerns that the government is seeking to silence dissent as Putin -- who has been president or prime minister since 1999 -- heads into a new six-year term.
Police briefly stopped Navalny and instructed him to avoid statements or actions that "do not correspond to the agenda of the gathering," which was held with the permission of the authorities.
Navalny told RFE/RL that he is very happy that the gathering was permitted by the Moscow authorities.
Navalny addressed the protesters, harshly criticizing the move by the government to block Telegram.
He said that police ordered him not to call on the protesters to join another rally scheduled by him for May 5.
"Therefore, I call you all NOT to take part in the rally on May 5," Navalny said sarcastically.
Navalny has not received permission to hold the rally, which the ardent Putin critic has dubbed "He Is Not A Tsar!"
Telegram supporters have been protesting since April 16, when state media regulator Roskomnadzor started enforcing a court ban on the app over its refusal to hand over encryption keys to the FSB.
Telegram has cited privacy concerns and called the FSB's demand unconstitutional. It has promised to keep the app running despite the ban.
Telegram co-founder Pavel Durov, who lives in self-imposed exile abroad, called the rally "unprecedented."
"I am proud that I and these people were born in the same country. Your energy changes the world," Durov wrote on the Vkontakte social-media site.